Photonics / Fotonik

Permanent URI for this collectionhttps://hdl.handle.net/11147/2590

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Subject: search.filters.subject.Piezoelectricity

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Thickness-Dependent Piezoelecticity of Black Arsenic From Few-Layer To Monolayer
    (Elsevier, 2023) Akgenç Hanedar, Berna; Yağmurcukardeş, Mehmet; Ersan, Fatih; Altalhi, Tariq; Yağmurcukardeş, Mehmet; Yakobson, Boris; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Ultra-thin forms of black phosphorus (b-P) have been widely investigated due to its unique properties arising from the in-plane anisotropy in its crystal structure. Recently, two-dimensional (2D) forms of black arsenic (b-As) have also been added to the 2D family. In this study, the thickness-dependent structural, electronic, and piezoelectric properties of layered b-As are investigated by means of ab-initio calculations. The structural optimizations confirm the van der Waals type layered structure for both these structures. In addition, increasing the thickness is shown to result in the decreasing of the band gap arising from the confinement of electrons in the layers. In contrast to the case of b-P, it is revealed that a transition from indirect-to-direct band gap behavior can be found in b-As which can be important for optically identifying the single-layer structure. Moreover, the piezoelectric properties are investigated as a function of the number of layers. It is shown that while a single-layer of b-As does not exhibit piezoelectric features, even in the case of bilayer structures the piezoelectricity is created. Our results revealed the strong in-plane anisotropy in piezoelectric coefficients for the three-layer and thicker structures. We have shown that the out-of-plane piezoelectric properties can be achieved by non-centrosymmetric features in the out-of-plane direction in thicker structures of b-As.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Functionalization of Single-Layer Tas2 and Formation of Ultrathin Janus Structures
    (Cambridge University Press, 2020) Kahraman, Zeynep; Kahraman, Zeynep; Yağmurcukardeş, Mehmet; Yağmurcukardeş, Mehmet; Şahin, Hasan; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Ab initio calculations are performed to investigate the structural, vibrational, electronic, and piezoelectric properties of functionalized single layers of TaS2. We find that single-layer TaS2 is a suitable host material for functionalization via fluorination and hydrogenation. The one-side fluorinated (FTaS2) and hydrogenated (HTaS2) single layers display indirect gap semiconducting behavior in contrast to bare metallic TaS2. On the other hand, it is shown that as both surfaces of TaS2 are saturated anti-symmetrically, the formed Janus structure is a dynamically stable metallic single layer. In addition, it is revealed that out-of-plane piezoelectricity is created in all anti-symmetric structures. Furthermore, the Janus-type single-layer has the highest specific heat capacity to which longitudinal and transverse acoustical phonon modes have contribution at low temperatures. Our findings indicate that single-layer TaS2 is suitable for functionalization via H and F atoms that the formed, anti-symmetric structures display distinctive electronic, vibrational, and piezoelectric properties.